Question

y^iv+y^ii=3x^2+4 sinx-2 cosx​

Answer 1

Answer:

I don't know

Step-by-step explanation:

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Answer 2

Answer:

Here is the differential eqn I am having trouble with

y′′′′+y′′=3x2+4sinx−2cosx

So I am supposed to solve this by method of undetermined coefficients.

So the characteristic equation should be m4+m2=0

so m=0 (repeated) and m=±i (euler identity)

yh=c1+(Acosx+Bsinx)

Now to find the complete solution I need to find yp.

So according to the Sum rule y=yh+yp1+yp2

to get yp1,

So I am now supposed to first solve y′′′′+y′′=3x2

So let a sol be

yp1=K2x2+K1x+K0

So,

y′p1y′′p1y′′′′p1=2K2x+K1=2K2=0

This is the part where I get stuck Substituting values of y to find the coefficients we get

2K2=3x2

K2=0?

There must be something wrong here.